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Introduction of a New Non-Invasive Pressure Sensor for Common-Rail Systems 2002-01-0842

In the last decade direct injecting diesel engines have become more and more important in the automobile industry. Common-rail systems allow to shape the injection curve to reduce emissions, to get a better fuel economy and to provide more comfort. For this the common-rail system itself must be improved. A fundamental problem of the common-rail technology is to measure the exact injected amount of fuel, depending on the absolute rail pressure and pressure oscillations on the rail. Another problem is the delay between trigger signal of the injector and opening of the injector that results in a non-smooth idle speed.

One idea to solve this problem is to install a pressure sensor in front of the injector. Due to costs and density problems under high pressure, a simple, non-invasive sensor is preferred. The sensor introduced in this paper is based on the magneto-elastic effect and does not involve any mechanical elements. A description of the functional principle of the sensor and the influence of pre-magnetization on the output signal is presented, furthermore, different designs of this sensor will be introduced and discussed. A summary in the field of application of this sensor will show the possibilities for such sensors systems.